The Clinical Core will continue to provide a registry of well characterized patients and control subjects to foster clinical and basic scientific research on Alzheimer's disease (AD). To capitalize on the unique strengths and research interests of Emory investigators, the following major cohorts of patients will be recruited and followed: (1) probable AD; (2) Parkinson's disease (PD) without dementia; (3) PD with dementia (PDD); and (4) control subjects without evidence of cognitive or motor impairment. African-American subjects will continue to be recruited through our Satellite Clinic and other sites, maintaining 30% participation in each of our registry cohorts, in parallel with the proportion of African-Americans in our community. Blood will be obtained on patients and control subjects for characterization of mitochondrial DNA, apolipoprotein E genotyping, and other analyses as well as the establishment of lymphoblastoid cell lines by the Molecular Core. Comprehensive and standard neurological and neuropsychological assessment designed to evaluate multiple cognitive and behavioral domains will be performed along with clinical evaluation and quantitative neurophysiological tests of motor function. These data, in combination with molecular and eventual neuropathological information will be a valuable resource for the multidisciplinary group of Emory investigators exploring the heterogeneity of AD, PD, and the overlap among these and other neurodegenerative disorders.